Shimano Ultegra is a bit more refined that Shimano 105, with lighter materials in some areas and details like more durable coatings on some parts Both 105 and Ultegra are 11-speed systems and there are many more similarities between them than differences. Although Ultegra is more expensive, all of the same technology features in 105, and you operate them in exactly the same way.

For mountain bikes, 12-speed cassettes are largely the default for higher-spec groupsets, paired with a single-ring chainset. It's also worth mentioning the dedicated cyclo-cross chainsets which have reduced chainring sizes (Shimano's FC-CX50 offers 46, 36 chainrings). We awarded both Shimano 105 and Ultegra 10/10 for performance, and we give out very few 10/10 marks. We marked Ultegra 7/10 for value while giving 105 9/10 courtesy of offering a very similar level of performance at a significantly lower price. That might or might not be important to you. Definitely agree with this; the 50/34 and 11-34 combination does give you some good winching gears but a sub-compact would be what i'd go for on my tripster if it were available. Shimano's SPD-SL system is well-established, and the PD-R7000 pedal is an incremental development over the last incarnation. The new design of the carbon fibre reinforced resin pedal body has managed to shave a bit of weight, though; the weight is down 25g to 265g, only 17g more than the Ultegra pedals. There's a big range of tension available, so you can be securely or loosely held to your bike depending on your preference. The SPD-SL system is my personal favourite for road cycling, but different pedals suit different folks. The pedals come shipped with SM-SH-11 (yellow) cleats, which have 6° of float. There are two other options: blue, with 2° of float, and red, with no float at all.The differences are minor and mostly come down to materials. This results in Ultegra components being a little lighter than their 105 counterparts. No single Ultegra component is massively lighter and the small savings add up to just 191g across a whole groupset (the figure could be a little more or a little less than that depending on exactly which options you choose). I currently run a full ultegra 6700 groupset with a 105 5700 short cage rear derailleur on my Planet X Nanolight. I have an 11-34 cassette with a 50-33 frankest. The 33 inner is a TA Specialities item and the 50 ring is a Strong light CT2. My frame has very short chainstays and everything shifts superbly, the Stronglight rings ramps and pins are better than Shimano ! Nevertheless, the weight difference is surprisingly small, less than 200g for a typical ensemble; most of the difference is in the brake/shift levers and chainset There are new rear derailleurs on the market that are identifiable as being compatible because they have a ‘520% range’ graphic printed on the derailleur cage. SRAM Eagle AXS rear derailleurs are compatible with the new 10-52 cassettes. The executive summary: Ultegra is a bit lighter and more durable; it's the way to go if you're racing or logging mega miles and can't afford Dura-Ace, but for most riders 105 does the job admirably

The crank is a lever, and as with all levers, the longer the lever from effort (your foot) to load (the bb axle), the less effort you need per unit of movement achieved. In response to your question, basically the spec charts show that the materials used in Dura-Ace, Ultegra and 105 vary depending on the product. Broadly speaking all products use anodized or painted aluminium but more CFRP is used at Dura-Ace level and more steel is used at 105. For example see here:

Shimano 105 R7100 Di2 Groupset

The new design is compatible with direct mount frames, although there aren't many of those in the road sector right now. Now that 12-speed road bike groupsets exist, cassettes can have a larger range and the jumps between each gear can be relatively small. Where an 11-28 cassette would have once been considered a large training cassette, it now sits at the lower end of the typical range for road. Simon Bromley / Immediate Media However, as groupset manufacturers have jumped onto the gravel bandwagon, there are now gravel-specific gearing options available on the market.